Actual metal coverage at the neck is critical for flow-diverting stents in treating intracranial aneurysms.

We read the interesting article by Schneiders et al, entitled “A Flow-Diverting Stent Is Not a Pressure-Diverting Stent.” The authors measured intra-aneurysmal pressure before, during, and after placement of a flow-diverting (FD) stent and found that the pressure inside the aneurysm momentarily decreased during placement but was restored to baseline values within minutes. They agreed with the argument that the use of an FD stent for treatment of intracranial aneurysms should be combined with insertion of coils in the aneurysmal sac. After carefully observing the conventional angiogram in their article, we found that the included angle of the radiopaque longitudinal markers of the stent at the neck was approximately 60°. Therefore, the stent was partly elongated at the neck of the aneurysm. The metal coverage rate (MCR) of an FD stent can change as a result of either compression or stretching. The MCR ( ) and pore density of the stent can be calculated according to the following formula: